Geoscience Reference
In-Depth Information
Land air heated by subsidence
Mixture of land and
sea air heated by
subsidence
Sea
breeze
front
Sea air heated
by subsidence
Heated land
air
Heated sea air
Cool sea air
Sea
Land
Figure 8.15 Schematic representation of a sea breeze when the geostrophic wind is light. They can extend inland over 100 km
under favourable conditions.
The higher temperature over the land by day generates
a weak low-pressure area. As this intensifies during day-
time heating, a flow of cool, more humid air spreads
inland from the sea, gradually changing in strength and
direction during the day ( Figure 8.15 ). At night the reverse
circulation evolves, with a flow of air from the cooler land
to the warmer sea, though as the temperature difference
is usually less, and the atmosphere stable, the land breeze
is weak. At higher levels we find a flow in the opposite
direction, compensating for the surface land or sea breeze.
Large lakes, such as the Great Lakes of North America and
Lake Victoria in East Africa, show breeze systems of this
nature.
In tropical areas the strength and reliability of the sea
breeze bring a welcome freshness to the climate of the
coastal margin and its effects can extend up to a couple
of hundred kilometres inland.
KEY POINTS
1
The atmospheric processes of radiation, convection, evaporation and advection interact with the variable
nature of the ground to produce a mosaic of microclimates. Distinctive effects can be found at a wide variety
of scales in increasing size, from the microclimate of a single leaf, through crops, forest, valley slopes,
urban areas and sea-land breezes. They are the product of the variable interaction between the energy
exchanges and the ground surface.
2
In most cases there is no firm boundary between scales: the micro and local climates form part of a
continuum or spectrum from smallest to largest. Certainly within the larger scales like urban climates there
would be innumerable microclimates resulting from surface modification. This diversity makes their
investigation fascinating.
 
 
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